Building 5 Coffee Can 3d Led Emergency Lights

[sparkplug1947]

Thanks in advance for advice on building these low cost but long running, bright
3d or 6 volt type lights for black out or emergency use. I have all the materials except the bulbs. Is Cree the way to go or is there better leds? I want to use
simple coffee can type containers for the room lights. I have the switches, wires, and can epoxy or solder them on with low temp. Need advice on regulation, or would direct drive or resistors be better for the longest and brightest runtime? Can do without reflectors but any suggestions will be appreciated. What about different battery types, I have containers of all sizes.
Thanks again for all your input on this great forum!!

 

[clg0159]

A couple of guidelines for you.
1)If you are going to use high powered LEDs and run for extended periods you must heatsink them(check the forum for info)
2)For longest runtimes use direct drive, but to maintain higher levels of light at the cost of shorter runtimes use regulation of some sort(again all this info can be found within the homemade/mod forum)
3)Different emitters project light at different angles so you need to consider that before choosing the emitter(check LED forums and mod forums)
-CPF's provide you with all the info. you need so be patient and read alot if you want to get it right the first time. Have fun and welcome to CPF!

 

[Gunner12]

Direct drive would be the most efficient but the LED draws a lot of power with a 4.5v Vin. The Cree LED would draw at least 2 amps at 4.5v. It would stop emitting useful light at under 2.7v.

I would suggest a good driver and 2 1.5v batteries. This driver is pretty efficient. You could also short out the main chip to remove the modes. It will run at under 1.2v.

With the driver set at 1.5v, there is around a 1.6 watt input at 2.4v. 2 1.5v D batteries have around 60 watt power, so that would mean at least a day's worth of continuous runtime or around 5 hours on 2 AA batteries. That is not including the long tail of lower level light output. You could also set the driver to an even lower output to increase runtime.

From my experience, a Cree XR-E P4 produces enough light at 0.5 watt to easily navigate around a living room. That is pointing the light at the ceiling and loosing some output to the paint. If you want enough light to read in a room via ceiling bounce of light, try making three of those lights, setting the driver to 1-1.5 watt and using the Cree XR-E Q5 LED(the brightest one out right now).

If you are just pointing the light at a book, then one 1 watt setup is enough.

If you really want a long lasting dim light, look at building a Joule thief.

The Cree XR-E Q5 is the brightest LED right now, the Rebel 100 is a bit more efficient but it is also much harder to solder. The Cree Q5 is available at DX for $10. The lower output P4 can be bought at $5. Also have a good heatsink for the light to prevent overheating. at 1 watt, a CPU heat sink is enough, you just need termal paste/epoxy to ensure a good thermal path.

The Seoul P4 LED and the Rebel 80 (Around Cree P4 performance, Rebel 100 is more efficient, around Q4-Q5) LEDs are also available on stars (easiest to solder)

Any of the newer LEDs would work for you application and I would pick regulated for your task.

:welcome: